Considerations include:

Your existing operations, and how the new intermediary can fit with them. For example, if you want to keep an existing sales operation (such as a sales force, telesales team or online sales), you will need an intermediary who is happy to work alongside that.

How closely you want to be involved in the sales process. It can be easier to have more control over how an agent handles sales.

What type of relationship you want to have with the ultimate customer. Using a distributor may distance you from the ultimate customer.

Agents are often preferable for making high value, complex or bespoke sales. You will also need to use an agent if you want to sell a service which you must deliver. Distributors, such as wholesalers, are often used for making lower value sales of relatively straightforward products.